Keyence’s Electromagnetic Interlock Switch Solution for Safety Fencing and Guarding

September 26, 2022 by Shawn Dietrich

Keyence releases new safety-rated interlock switches for monitoring and locking the position of guarding and fencing. Unlike traditional door switches, the GS-M series switches use electromagnetic technology.

The new safety interlock switches from Keyence, the GS-M series, are different from traditional interlock devices: they are a keyless design that uses a built-in electromagnet, making them more compact and easier to lock.


safety interlock switches for guard doors and safety fencing from Keyence

Keyence announces the release of safety interlock switches for guard doors and safety fencing. Image used courtesy of Keyence


Safety Switches For Guard Doors

Any machine with moving components such as robots, servo motors, or pneumatic positioners will have guarding or fences to protect operators and people. The guarding or fencing needs to be detected when it is removed or opened. Typical safety switches are safety-rated limit switches or flag-style safety switches. They will have dual redundant contacts inside that will transmit an electrical signal back to the safety controller or safety relay when closed or opened. 

Some doors are required to be locked, so some door interlocks will have a key mounted on the door and the locking mechanism is mounted inside the machine. When the door is closed, the key fits into the mechanism and the solenoid actuates the lock. These styles of door locks and safety switches have been used for many years with great success, but they come with their problems. The key needs to be aligned with minimal misalignment, and the keys can be faked out by putting a spare key into the mechanism. The locking mechanism also typically takes up a lot of space within the door frame. 


traditional door switch versus Keyence's electromagnetic door switch
A traditional door switch (on the left) vesus Keyence’s electromagnetic door switch (on the right). Images adapted and used courtesy of Keyence


GS-M Series Door Interlock Switches

The GS-M series door switch from Keyence uses a powerful electromagnet to detect and hold the door closed. By using a magnet, the overall size of the door switch is greatly reduced from typical door switches. The GS-M also has a greater misalignment factor—up to 4 degrees of misalignment is allowed. To assist the operators and integrators, there is a highly visible indicator that shows if the door is closed, closed and locked, locked, or if the door is open. Using this indicator will aid in aligning the permanent magnet with the electromagnet. 

The GS-M can use a wire-saving unit GS-T01 which allows up to eight GS-M interlocks to be cascaded together while still giving individual feedback from each interlock device. The GS-M comes in two models: the 500N model GS-M5, and the 900N model GS-M9. These models have different hold forces to accommodate different weighted doors. A small, simple light door may only need the 500N interlock while a much larger heavier door would require the 900N model.

The interlocks can be mounted to accommodate swing doors or sliding doors. To prevent bypassing or tampering, the GS-M interlocks have two modes: low and high. The low mode will allow any GS-M actuator to activate the interlock, while the high mode will only allow one specific actuator to activate the interlock. 


Keyence's GS-M magnetic door interlock switches

Keyence’s GS-M magnetic interlocks are safer and simpler to integrate than typical door interlocks. Image courtesy of Keyence


Integrating Magnetic Interlocks

Any safety component that is installed on a machine will need to be configured and tested. For some equipment, this can take days of troubleshooting and aligning. Typical door interlocks with the key and mechanism require extensive alignment and space within the door itself.

With the Keyence GS-M door interlock, there is only an electromagnet to mount and a permanent magnet that gets mounted on the door. Using coded magnets allows for safer equipment because operators or technicians will not be able to bypass or tamper the door lock. These magnetic interlocks are the compact solution the industry has been waiting for.